In recent years, to recycle waste materials generated at construction sites, civil engineering sites and the like, self-traveling crushing machines are installed at construction sites and the like to crush the waste materials generated during work operations so that the waste materials are recycled as materials for work operations.
An example of a self-traveling crushing machine includes a traveling device and a jaw crusher installed thereon. The jaw crusher produces aggregate having a predetermined particle-diameter from a to-be-crushed object by compression force and shear force while supplying the to-be-crushed object such as a concrete mass to a V-shaped space formed by a fixed jaw and a movable jaw and swinging the movable jaw relative to the fixed jaw.
Because such a jaw crusher employs compression force and shear force to crush the to-be-crushed object, the device body of the jaw crusher including the fixed jaw and the movable jaw may be overloaded depending on operating conditions of an operator and characteristics of the to-be-crushed object.
In view of the above, the conventional jaw crusher includes: a toggle plate that interconnects the swinging movable jaw and the device body having the fixed jaw; and an overload escaping section in which the toggle plate buckles to let go the load on the movable jaw when the movable jaw is overloaded to a predetermined extent (e.g., see, Patent Document 1).
Another overload escaping section includes, instead of the toggle plate, a hydraulic cylinder with a close fit mechanism in which strokes are changed by hydraulic pressure when the movable jaw is overloaded (e.g., see, Patent Document 2).    Patent Document 1: JP-A-06-23287 (FIGS. 1 and 4)    Patent Document 2: JP-A-2003-53203 (FIG. 1)